1. Technical Field
The present invention relates to a structure, a method of manufacturing the structure, and a liquid droplet discharge apparatus, and more particularly to a structure such as an inkjet recording head configured by as a result of a recording head unit that discharges ink droplets from nozzles to record an image on a recording medium being retained on a base plate, a method of manufacturing the structure, and a liquid droplet discharge apparatus applied to an inkjet recording apparatus or the like disposed with a structure comprising an inkjet recording head.
2. Related Art
In conventional partial width array (PWA) inkjet recording apparatus that reciprocally scan a head, there has been a limit on increasing the number of nozzles because when the number of nozzles is increased for high-speed printing, the mass of the head also increases and the burden on the head scanning mechanism becomes larger. Further, this becomes disadvantageous for increasing speed because an excessive scanning distance arises when inverting reciprocal scanning.
As a method of addressing these issues, a non-scanning type full width array (FWA) inkjet line head corresponding to the width of the recording medium is already known where numerous nozzles are disposed at a pitch that is the same as the resolution in the width direction of-the-recording medium. Yet when a line head disposed with numerous nozzles is manufactured as an integral head, there are problems in that the yield drops and expensive manufacturing equipment such as a large diameter silicon process apparatus, for example, becomes necessary.
Thus, technology has been disclosed where plural head units having a relatively small number of nozzles are connected in a line to increase the length of the head.
This technology has a system where the element base plate, which has the lowest yield of the constituent parts, is divided into units and manufactured, so that it becomes necessary to mutually position/fix the adjacent units with high precision.
When, for example, the recording head units are positioned/fixed to a long base plate using an adhesive or positioned/fixed to a spacer member configured such that it is attachable to and detachable from a long base plate, productivity becomes an issue when a room temperature-curing adhesive is used because it takes a long time for the curing. Positional displacement, which occurs due to differences in thermal expansion, becomes an issue when a thermosetting adhesive is used because the coefficients of thermal expansion of the constituent members are different.
In contrast, when a light-curing adhesive is used, the amount of time required for curing can be shortened over that of a room temperature-curing adhesive, and positional displacement resulting from differences in the thermal expansion of the constituent members occurring during high-temperature heating such as encountered with a thermosetting adhesive is also suppressed. Thus, a light-curing adhesive is suited to a structure configured as a result of bonding/fixing such a unit to a base plate or a spacer member. Further, in order to achieve more high-precision positioning/fixing using a light-curing adhesive, it becomes important to reduce as much as possible temperature rise and temperature fluctuation accompanying light irradiation and to suppress stress resulting from contraction when the adhesive is cured.
However, particularly in a line head where plural recording head units having nozzles formed in a matrix are positioned/fixed and arranged with high precision, sometimes units having a special planar shape (a substantially parallelogram shape) are used as a matter of convenience, such as in terms of the volume occupied by the line head portion in relation to apparatus size and the nozzle arrangement. In the case of such units having a special shape, there is a demand for improvement because sometimes the effect of heat at the time of light irradiation causes the amount of displacement of the unit portions (nozzles) to change depending on the irradiation position and irradiation energy.
Further, in the case of a line head where plural recording head units are arranged, it is preferable to surface-bond the recording head units and the base plate or spacer member retaining the recording head units in order to obtain high bonding strength at the bonding/fixing portions between the base plate or spacer member and the recording head units. However, because it is necessary to align the nozzle surfaces of the recording head units, a large gap must be disposed in the bonding/fixing portions such that it can absorb the height tolerance (variations in height between the recording head units) of the recording head units using the nozzle surfaces as a reference. For this reason, the amount of adhesive in this gap increases, it becomes easier for positional displacement and slanting of the recording head units resulting from contraction when the adhesive is cured and for variations in the displacement amounts between the recording head units to occur, which become a problem in terms of positioning/fixing the plural recording head units with high precision.